Alignment of scans in dynamic PET study using stackgram domain

A new alignment method for sequences of 3D tomographic data is described. This kind of demand is e.g. in list mode acquisition of positron emission tomography (PET) or gated PET, assuming that distributions during separate scans are nearly equal. The alignment is performed locally in the stackgram domain, which is a stack of back-projected projections. The signals parallel to the stackgram´s vertical axis are locus-signals or sinusoids which form the sinogram. The locus-signals can be processed independently in the stackgram domain. Transformation from the sinogram to the stackgram domain and back can be implemented without loss of information even in the discrete case. The new local alignment method is based on similarity comparisons between locus-signals in 3D neighborhood of sequences of the stackgrams. The final results are aligned sinograms, or alternatively, FBP reconstructed images. The new method does not require any external movement tracking system or landmarks and it can be implemented to be fully automatic. In this paper, the method is tested using simulated data.